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srnemrcs'non' forming part of Letters known as white slating, yvhich consists of a compound of waterla and a metallic oxide added thereto to form a tooth, to enable the -tablet to take the pencil freely. Such a com- 'pound is entirely non-elastic, and it is found that upon dryingithe slated surfaces are filled with innumerable fine cracks or fissures, into which the lead of the pencil is rubbed in erasing. thereby in a very short time rendering the tablet unit for use.

The object of my invention is to furnish a slating compound for-such tablets having the 25 required degree of elasticity, which, when spread upon a surface, and dried, forms aa smooth, eyen, and unbroken surface of great durability. 1

To this end the invention consists in a slat- L uwm flied answers.

SLATING COMPOUND FOR .ERASABLE TABLETS. 7

ram No. 225,133, dated March 2, 1880.

ing compound composed of a solution of wa- 3o {er-glass, oxide of zinc, and silicate of magnesnmn- I takeabout one (1) quart of water solution thus formed I mix aBB'uE one-(Uponnd 3 5 Lof pure oxide of zinc powdered and about --ed smcm'e vi 1 e sium. When thoroughly mix a compouu o the consistency of paint is formed, which may be readily applied to sheets of stifl'paper, 40 board, or other material by means of a brush or otherwisef-v This compound, when dried, forms a smooth, even, and unbroken surface, from which pencil or other marks may be easily eragsglgsfihd'as said surface contains no crack's'drfissures into -which the lead of the pencil is rubbed tablets slated with such 00!!!- pound are very durable, and will, #hotbecnme discolored by long use.

Vhat I claim as my invention,-a nd desire to secure by Letters Patent, is-

The slating compound composed of waterglass, oxide of zinc, and silicate of magnesium, substantially as herein specified.

HENRY W. HOLLY.

v Witnesses HENRY T. BROWN, FR D Hams.

LMIVHNLH ZZJ/33 less of about thirty-nine degrees 39; Fannie an add one (1) quart of water. it t e' 

